WEAK VORTICES AT VERTICAL INTAKES.

Weak, free surface vortices at vertical intakes with a headrace channel are defined by the first observance of a persistent dye core upon dye injection. Dimensionless parameters describing free surface vortex flows are used in an analysis of experimental data. The experimental results indicate that a large dimensionless submergence is required to avoid weak vortices at vertical intakes. Most vertical intakes will therefore require some type of antivortex device if weak vortices are to be avoided. The required dimensionless submergence is also highly dependent upon approach flow angle and headrace length/width ratio.